The Promotional Effects of Carbon Nanotube on Fe5c2-Zno Catalysts for Co2 Hydrogenation to Heavy Olefins

Abstract

The multi-walled carbon nanotubes (MWNTs) supported Fe-based catalysts were prepared by co-precipitation and incipient wetness impregnation methods. The physicochemical results demonstrated that the addition of MWNTs had significant influences on the morphology, phase structures, reduction and adsorption behavior, and hence the catalytic performance of the catalysts during CO2 hydrogenation to olefins. Furthermore, the addition of MWNTs to Fe-based catalysts inhibits methane and CO formation and favors a higher selectivity to olefins. With the addition of MWNTs, the selectivity to the heavy olefins (C5-C8=) over FeZnNa, FeZnK, and FeZnRb catalysts increased from 27.1-32.2, 27.0-31.1, and 24.2-28.6%, respectively. The results revealed that superior selectivity of heavy olefin on the MWNTs supported Fe-based catalysts might be accomplished by the electron-donating ability of the MWNTs surface, the presence of extra Hägg carbide, and higher adsorption strength with light olefins. MWNTs supported catalyst also exhibited excellent stability during the 100-h test at 593 K.

Keywords: CO2 hydrogenation, multi-walled carbon nanotubes, iron-based catalyst, graphite carbon, heavy olefins